Apparatus for controlling the charge of storage batteries



H. MITCHELL Nov. 10, 1936.

APPARATUS FOR CONTROLLING THE CHARGE OF STORAGE BATTERIES 2 Sheets-Sheet 1 Filed NOV. 5, 1934 jfaro-Zdflfic/zeZZ BY myw za ATTO R N EYS Nov. 10, 1936.

H. MITCHELL APPARATUS FOR CONTROLLING THE CHARGE OF STORAGE BATTERIES Filed NOV. 5, 1934 2 Sheets-Sheet 2 ATTORNEYS Patented Nov. 10, 1936 UNITED STATES APPARATUSFOR CONTROLLING THE CHARGE or STORAGE BATTERIES Harold Mitchell, .winnipez, Manitoba, Canada Application November 5, 1934, Serial No. 751,660

1 Claim.

The invention relates to electrical devices for automatically controlling the charging of storage batteries.

The principal object of the invention is to provide a device adapted particularly for use on motor vehicles and connected across the generator .for controlling the current output to. the battery, thereby protecting the battery from damage by overcharging especially while driving on long trips at high speed.

It is well known that if the charging rate of a generator is high damage may result to the storage battery or to the generator particularly when long trips at comparatively high speeds are undertaken. To offset this danger it is a common practice among many motorists to keep their headlights-burnings even inthe daytime.

However, this is but a makeshift and is a matter of guesswork;

9 To overcome this objection I have devised the present invention which has for an important object the provision of a device which may be adjusted according to the proper voltage of a fully charged battery and which will then automat- 5 ically reduce the charging rate regardless of cir cumst'ances, which will then automatically reduce the charging rate when the voltage of the battery reaches the certain predetermined maximum, andwhich will permit the normal charging rate to berestored when, the dangerous overcharged condition is eliminated.

Another object of the invention is to provide a control device which will eliminate all guesswork.

i insure starting or easy starting at very low temperatures.- v

Another object of the invention is. to provide a device of this character which may be used as standard equipment by manufacturers or which v may be attached to an existing car in a short time and without any material alterations in the wiring or in any other part of the electrical apparatus.

An additional object is to provide a device of this character which will be simple and inexpensive to make,.assemb1e and install, rugged in construction so as to be capable of withstanding the shocks and jars incident to travel without detrimental effects, which will be easy to set or adjust, which will be durable in service and also 5 a general improvement in the art.

. ing within which the'device is enclosed,

Figure 2 is a side elevation of the control device with the casing removed,

Figure 3 is a top plan view thereof,

4 Figure l is an end elevation with parts broken away and in section,

Figure 5 is a vertical cross sectional view taken centrally of the device or on the line 5-5 of Figure 3,

Figure 6 is-a diagram showing the electrical circuits. 4

Speaking generally, I. have shown the device as comprising a pair of electro magnetically op- 'erated relays appropriately connected in the charging circuit of an automobile, or in fact any other storage battery charging system, and

connected with a variable resistance. While the construction may be varied in numerous respects, I have shown the device as comprising, in detail, a pair of electro-magnets I 0 and II preferably of the horseshoe type, having their legs extending through a base or sub-panel I 2 of non-magnetic material and also through a panel l3 having the same characteristicsthe ends of the legs projecting beyond or above the panel l3 so as to serve as pole pieces, the ends being represented 40 as carrying nuts I 4 which serve to support not only the electro-magnets themselves but also the other parts of the apparatus. In accordance with patent practice it is not necessary to describe the number of turns or the size or. the character of the coils I5 and I6 of'these respective magnets as such details depend entirely upon the requirements of proper design.

Pivoted at I! upon brackets l8 rising from the panel I3 is an armature l9 positioned to be. attracted by the electro-magnet Ill and it is intended that this armature be so constructed and arranged that under normal conditions it will be unaffected by the magnetic pull exerted by the magnet l0. It will be noted that the armature is is pivoted intermediate its ends and that its rear end is pulled downwardly by a coil spring 23 anchored to the sub-panel or base l2 and connected with an adjusting screw 2| which passes freely through the panel l3and which is ad- Justably connected with the armature l3 by means of nuts 22. The lower end of the spring 23 is represented as'anchored to the base l2 by a screw or bolt 23 which passes through insulating washers 24 and an insulating bushing 25 and which is equipped with a nut 23.

The free end of the armature l3 carries an adjustable contact screw 21 designed to cooperate with a contact 23 mounted upon and insulated from the panel l3. A stop screw 23 may also be' position by a tension spring 33 anchored to the base l2 and connected with an adjusting screw 34 passing, freely through the panel l3 and adjustably connected with the armature by lock nuts 35, a stop screw 33 being provided beneath the armature for, limiting its downward movement under the influence oi the spring 33. The lower end of the spring 33 is anchored to the base by means of a bolt 31 which passes through insulating washers 33 and an insulating bushing 33 and which is equipped with a nut 43. The free end of the armature 32 carries an adjustable screw contact 4| adapted to cooperate with a contact 42 mounted upon and insulated from the panel i3.

Located between the two electro-magnets l3 and H is a variable resistance indicated as a wholeby the numeral 43 and formed oi any desired length or number of turns of wire of appropriate resistance material. Figure 5 shows, in detail, the mechanical construction of this variable resistance though it'should be understood thatthere are no particular limitations as to the details. Actually this variable resistance is represented as including a number of stretches 44 oi coils; anchored at spaced points to the base l2 by bolts 45 which pass through insulating bushings '43 and which are equipped with nuts 41. These coils or stretches of the variable resistance are anchored in a similar manner to the panel l3 bybeing connected'with bolts 43 which pass through insulating bushings 43 and which are equipped with binding nuts 53.

It is intended that the springs 23 and 33 have a common ground connection and I have therefore represented such a connection at 3|, this connection being conceivably a strip, a bus bar or, simply, a suitable wire connected with the bolts 23 and 31 by means of the nuts 23 and 43, respectively, thereon. The resistance is intended to be set, in advance, in accordance withthe requirements of the particular generator and battery with which the device is used and it is for this reason that the various binding nuts 53 are provided so as to permit this regulation 'or 7 adiustability by enabling as many as may be desired oi the lengths or stretches 44 of resistance 53 from which a jumper 54 extends which may be connected with a selected one oi the other binding posts 53 so that the amount oi resistance may be easily regulated.

It is desirable that the variable resistance 43 be shielded from the electro-magnets, and vice versa, and for this. reason I have disclosed an angular metallic member 55, of non-magnetic material, disposed between the resistance and the magnets, it being a convenient matter to anchor this shield in place by means of one or more of the binding posts 53 and also the bolts 23 and 31.

It is also intended that the device be enclosed within a suitable casing 53 0! non-magnetic material and having a detachable top 51 permitting access to its interior. This casing is disclosed as having a, suitable opening 53 ior the passage of the necessary conductors and is also provided with any suitable number of holes 53 for ventilating purposes so as to permit the escape of any heat generate by passage oi current through the variable resistance.

The electrical connections are as follows: The conductor 5| is grounded at 33 by being connected with the chassis oi the vehicle. Leading from the generator is a wire 3| which leads to the ignition oi the car and which is connected either directly or through a switch 32 with the storage battery 33 which has its other terminal grounded at 34. Connected with the wire II is a conductor 35-which is connected with a selected one of the bolts 45 which mount the lower ends of the elements of the variable resistance. Also connected with the conductor 35 are conductors 33 and 31, the former of which is connected with one terminal 0! the electro-magnet l3 and the latter of which is connected with one terminal 01 the electro-magnet II. The remaining terminal oithe electro-magnet I3 is connected'to the armature l3, while the remaining terminal of the electro-magnet II is connected by a conductor 33 with the contact 23. Leading from the contact 42 associated with the electro-magnet actual; electrical connections are disclosed in Figure 6 and as a matter of fact it is immaterial just where and how the binding posts, considered mechanically, are disposed on the panel l3 or on the base l2 as such details can be varied within wide limits, the only requirementbeing that the connections, diagrammatically considered, be as illustrated in Figure 3.

The device having been constructed as disclosed, the operation is as follows: while the average car batterylis called'a six volt battery.

volts. It is possible to utilize this factor to e!- iect my purpose. The electro-magnet I3 is connected permanently across the battery and the spring 23 is adjusted to apply sumcient tension to the armature 13 to hold the contact 21 out of engagement with the contact 23. Current willflow from the battery 33, switch 52, conductor 3|, conductor 35, conductor 33, through the electro-magnet l3, armature i3, spring 23' and conductor 5! to the ground 33. Adjustment of the spring" is such that when the voltage oi.

the battery is normal or sub-normal there will be insufllcient strength in the magnet ID to attract the armature I9. However, as the process of charging the battery continues,.in the usual manner, the voltage of the battery will reach full charge or will rise above normal, increasing the strength of the magnet III to such a degree that it will attract the armature I9 against the resistance of the spring 20, thereby bringing the contact 21 into engagement with the contact 28. Current will then flow from the battery 63, switch 62, conductor 6|, conductor 65, magnet ll, conductor 68, contact 28, contact 21, armature l9, spring 23, and conductor 5|, to the ground 60. This will energize the electro-magnet II and cause the armature 32 to be attracted against the resistance of the spring 33 so that the contact 4| will be brought into engagement with the contact 42. Current then flows from the generator conductor 6|, conductor 35, and will divide, a portion continuing through the magnets l and I l as above described and a portion passing through as much of the variable resistance 43 as is originally connected in the circuit and will pass from the resistance through the conductor 69, contact 42, contact 4|, armature 32, spring 33, and conductor 5|, to the ground 60. Throwing of the resistance 43 into the circuit in this manner will naturally convert a portion of the electrical energy of the generator into heat which is dissipated into-the air and the charging rate of the battery consequently lowered or cut out entirely until the voltage in' the battery is lowered to a normal condition whereupon there will be insumcient strength in 'the electro-magnet ID to hold the contacts 21 and 28 closed against the pull of the spring 23, and the spring 20 will then disengage the contacts 21 and 28, thereby breaking the circuit through the magnet so that the contacts 4| and 42 will open, resulting'in opening the circuit through the resistance. The actionis entirely automatic as it is governed by the electro-mag-' netio switches or relays. It is oi. course to be understood that the connections to the various points of the variable resistance 43 wilFdepend on various circumstances, such as the condition and type of the battery itself, the generator and in fact the entire electrical system. It will be seen that it is a simple matter to tap in as much or as little of the resistance as may be necessary to meet the requirements of the particular vehicle on which the device is used. It will be clear that by the automatic action .brought about there will be no necessity for the operator of a motor vehicle to keep his lights burning when travelling on long trips at high speeds in the daytime and it is equally apparent that there is noguesswork involved as the entire apparatus is associated armature. |9 is considerably greater than that between the core of the electromagnet H and its associated armature 32. The

' reason for this willbe readily apparent when it As a result very little pressure is brought to bear upon the contacts 21 and 28. However as only one-fourth of an ampere of current is required to magnetize coil II, this construction is satisfactory under actual service conditions.

However with respect to magnet cooperating with the contacts 4| and 42, a different condition exists, the magnet being the control that must supply current to the variable resistance 43 which current may be III or 20 amperes. It is necessary that the magnet ll be extended to within substantially one-sixteenth of an inch of its associated armature 32 in order to close the switch contacts 4| and 42 with considerable pressure to handle the large amount of current passing through the switch. This spacing of the core l4 and armature 32 has been found in actual practice to be critical to insure successful operation.

Another important feature of the invention,

disclosed in Figure 2, is that the armatures I9 operation and advantages will be readily apparent to one skilled in the art without further explanation.

While I have shown and described the preferred embodiment of the invention, it should be understood that the disclosure is merely an exempliilcation of the principles involved as the right is reserved to make all such changes in the details of construction as will widen the field of utility and increase the adaptabiliy of the device provided such changes constitute no departure.

from the spirit of the invention or the scope of the claim hereunto appended.

Having thus described the invention, I claim:

In apparatus of the class described, a pair of electro-magnets of the horseshoe type, a pair of spaced non-magnetic plates supporting the magnets, the legs of the magnets projecting through one of the plates to form pole pieces, a platelike armature for each electro-magnet, brackets pivotally mounting the armatures, the armatures being counterbalanced on their respective axes to resist vibration, coil springs connected to one of the non-magnetic plates and adjustably connected to respective armatures at the rear ends thereof, a switch contact on the front end of each armature, stationary switch contacts on one of the non-magnetic plates adapted to be engaged by the first-named contacts when the associated" magnets move the latter to circuit closing position'against the tension of their respective con trolling springs, a variable resistance comprising I a plurality of stretches of wire disposed between and anchored through both plates of non-magnetic material, binding nuts associated with said stretches, a jumper connecting certain of the nuts for permitting a predetermined number of the stretches to be connected in series,- a member formed of non-magnetic material disposed between said plates of non-magnetic material and between the magnets and the variable resistance for shielding the variable resistance from the magnets, the exciting coils of both magnets being connected in series, the terminal of one coil being connected to one of said stationary contacts and the terminal of the other coil being connected to the armature associated with the stationary contact just mentioned, both armatures being grounded through their controlling springs, the variable resistance being connected across the other stationary contact and the exciting coils oi the magnets, the poles of one of the magnets being spaced 8. less distance irom their associated armature than the poles or the other magnet are spaced from their associated armature, and stop screws on one o! the plates of non-magnetic material underneath the armatures for limiting downward movement of the armature: under influence 01 their controlling springs.

HAROLD m'mma. 

